The immunochemical properties of rat cerebral myelin subfractions and of isolated myelin proteins are under investigation. The interplay among extrinsic myelin basic protein (BP), intrinsic proteolipid protein (PLP), and Wolfgram protein (W) as they appear in glial and myelin membranes of rats of different ages is being looked to as a possibly important immunochemical feature, particularly with respect to conformation in the presence of glycerophospholipids, sphingolipids, and cholesterol. Through the use of sequential adsorption techniques involving I125-labeled antiserum IgG reagents (antimyelin, anti-BP, antiPLP, anti-W, antiphosphatides, etc.) the nature of the various isolated fractions of myelin and glial cell membranes is being analyzed. Through the use of I125-labeled protein fractions (BP, PLP, W, etc.) and specially developed radioimmunoassays, the specific and cross-reactive nature of the various reagent antiserums is being further analyzed.